Aneurysms are acquired lesions related to hemodynamic stress on the arterial walls at bifurcation points and bends. Saccular or berry aneurysms are specific to the intracranial arteries because their walls lack an external elastic lamina and contain a very thin adventitia—factors that may predispose to the formation of aneurysms.
An additional feature is that they lie unsupported in the subarachnoid space. In nonequatorial South America, 34% of 450 cases from Santiago (Chile) were cerebral hemorrhages and 12% were subarachnoid hemorrhages. Finally, in Buenos Aires (Argentina) the frequency of hemorrhages were higher among Argentinean natives versus white immigrants (34% versus 27%)
Treatement is • Remove large collections of blood or relieve pressure on the brain if the hemorrhage is due to an injury • Repair the aneurysm if the hemorrhage is due to an aneurysm rupture If the person is critically ill, surgery may have to wait until the person is more stable. Ongoing Research is being done at Subarachnoid haemorrhage centres.